1. Field of the Invention
The present invention relates to an ink jet recording head, a liquid storage container for containing liquid, and an ink jet recording apparatus, which discharges a liquid on a recording medium such as paper, or cloth.
2. Description of the Related Art
In general, a serial scan type ink jet recording apparatus performs recording by discharging ink on a recording medium from a recording unit, i.e. an ink jet recording head.
The ink jet recording apparatus has advantages in that the recording unit can be easily made compact, a high-definition image can be recorded at high speed, and the like.
In such recording apparatus, ink must be discharged in a timing that a desired image is formed on the recording medium according to the moving position of a carriage.
Therefore, the ink jet recording apparatus is generally provided with a linear encoder to detect the position of the carriage.
The linear encoder is stretched across in a moving direction of the carriage, and includes an encoder scale, which is a reference to detect a moving distance of the carriage, and a sensor attached to the carriage which detects a moving distance of the carriage.
FIG. 8 is a perspective view showing the configuration of a conventional recording apparatus.
The conventional recording apparatus includes a recording head 1, a carriage 2, a carriage board 3, a linear encoder sensor 4, and a linear encoder scale 55.
Further, the conventional recording apparatus includes a main body chassis 6, two guide shafts 7, a leaf spring 9, a screw 10, a timing belt 11, an idle pulley 12, and a driving motor 13.
The main body chassis 6 is a casing for the recording apparatus, and the two guide shafts 7, the idle pulley 12, and the driving motor 13 are mounted on the main body chassis 6, respectively.
The two guide shafts 7 are disposed in parallel with each other, and the idle pulley 12 and the driving motor 13 are disposed on the same side of the main body chassis 6.
Between the idle pulley 12 and a pulley (not shown) provided to the driving motor 13, a piece of the timing belt 11 is stretched across in parallel with the guide shaft 7.
Further, the main body chassis 6 is provided with the leaf spring 9.
The leaf spring 9 is fixed by the screw 10 to one side of the main body chassis 6 to which both ends of the two guide shafts 7 are attached.
One end of the linear encoder scale 55 is fixed to the side of the main body chassis 6, and the other end is connected to the leaf spring 9 so as to be disposed in parallel with the guide shaft 7 while being pulled by proper tension.
The carriage 2 mounted with the recording head 1 is supported by the guide shaft 7 so as to slide along the guide shaft 7.
A portion of the timing belt 11 is connected to the carriage 2, and by rotation of the driving motor 13, the carriage 2 can be moved along the guide shaft 7.
The linear encoder sensor 4 is fixed on the carriage 2 with the carriage board 3, and is arranged so as to nip the linear encoder scale 55.
When the carriage 2 moves along the guide shaft 7 driven by the driving motor 13, the linear encoder sensor 4 connected to the carriage 2 also moves along the linear encoder scale 55.
The linear encoder sensor 4 converts positional information on the liner encoder scale 55 into a pulse signal.
The linear encoder sensor 4 transmits the pulse signal to a main board (not shown) via a flexible cable (not shown) and the like from the carriage board 3, and to an arithmetic unit (not shown) on the main board.
The arithmetic unit controls the position and the speed of the carriage 2 based on the pulse signal.
There are various types of linear encoders, such as a magnetic type and an optical type. The linear encoder of the magnetic type has a magnetic sensor and a scale configured of a metallic shaft or a sheet material to which magnetic information is given at a constant pitch.
As the optical linear encoder, in addition to a light emitting element and a light receiving element, one type has a scale with dark and light patterns of a constant pitch. Another type has a scale with an uneven shape of a constant pitch, and so forth.
The various types of linear encoders above described have advantages and disadvantages, respectively.
The magnetic linear encoder has an advantage in that, even when there is a slight ink contamination, it does not affect the performance of the encoder.
On the other hand, there are disadvantages in that it is difficult to make the magnetic linear encoder of high resolution, and hard to widen a gap between the encoder scale and the encoder. In addition, there is a problem of accuracy in mounting, and the gap is prone to be clogged by matter.
Further, in the case of the magnetic linear encoder, caution is required in handling magnetic tools and the like.
In the optical type linear encoder, high resolution can be easily obtained, and it is easy to make the gap between the encoder scale and the encoder sensor relatively wider.
In addition, it can be easily assembled. However, there is the disadvantage in that the performance can sharply deteriorate by ink contamination.
With respect to the conventional recording apparatus which is described above, even in the case of the popular and low cost apparatus, high resolution and high accuracy have been noticeably achieved, and an apparatus has begun to appear which shoots ink at a pitch of 1200 dots per 25.4 mm (one inch).
In the case where ink is shot at such intervals, needless to say, an ink shooting speed is required to increase, and moreover, high resolution is required of the linear encoder.
Naturally, it is ideal to use a linear encoder having a resolution of 1200 or more dots per 25.4 mm for a printer having 1200 dots per 25.4 mm.
However, because of a limit to the cost and the size, a linear encoder has been often used in which 300 dots or 600 dots per 25.4 mm are multiplied.
In recent years, a linear encoder having 1200 dots per 25.4 mm can be made at a low cost, and such a type that can be used for the general printer has begun to appear.
However, the influence arising from a shift of the phase and the amplitude of the output signal of the sensor which is generated by the contamination of the parts by ink and the like has become apparent as the preciseness of the linear encoder is increased, and is not negligible.
U.S. Pat. No. 6,264,303 discloses a cleaning member which slides against the linear scale of the optical encoder and removes a surface contamination.
Japanese Patent Application Laid-Open No. 2000-141802 discloses a method in which the cleaning member abuts against and separates from the linear scale.
Japanese Patent Application Laid-Open No. 2001-121721 discloses a cleaning timing and the situation under which the cleaning is performed.
However, in the case of the optical linear encoder where a ray to be sensed is required to be focused at the sensor side in order to detect a position, the contamination of the sensor has much larger effect than the contamination of the scale.
Further, associated with high resolution of the linear encoder, the ink droplet to be used has become small, and as a result, minute ink (hereinafter referred to as ink mist) is generated that cannot shoot on the recording medium.
Since this ink mist is extremely minute, it is prone to soar to the position of the linear encoder associated with the movement of the carriage. Accordingly, there is a great possibility that the mist enters into the sensor of the linear encoder.
Thus, it has become evident that the sensor of the linear encoder is often contaminated earlier than the scale of the linear encoder.
As described above, in the conventional apparatus, even when the cleaning of the encoder itself is performed, if the ink mist adheres to the detection sensor, durability of the linear encoder deteriorates.
There have been also problems such as disarray of print images and shutdown of the apparatus due to a reading error.
With respect of the contamination of the encoder scale, the replacement thereof by periodic servicing or the cleaning of the surface by the user himself can be easily performed.
However, with respect to the contamination of the detection sensor of the linear encoder, since a light emitting unit and a light receiving unit are integrally configured, it is extremely difficult to perform the cleaning.
Further, since these units are configured integrally with the recording apparatus, it is not possible to replace the sensor of the linear encoder unless the recording apparatus is dismantled and taken out.
In the case where a replacement need arises, the user is forced to put up with an extreme inconvenience of sending the main body to the customer service department to replace the parts thereof.